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Frequency divided group beamforming with sparse spacefrequency code for above 6 GHz URLLC systems
Chanho Yoon(Chanho Yoon),Woncheol Cho(Woncheol Cho),Kapseok Chang(Kapseok Chang),Young-Jo Ko(Young-Jo Ko) 한국전자통신연구원 2022 ETRI Journal Vol.44 No.6
In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering.
Chanho. Ko,Seungho. Han,Minseong. Choi,Kyung-Soo. Kim 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
This paper attempts to implement an integrated path planning and tracking controller that generates optimal control inputs guaranteeing a collision-free path. This integrated scheme is achieved by unifying model predictive control (MPC) with a potential field for assigning collision risk. The target vehicle is an electrified autonomous vehicle that is capable of directly controlling traction and braking torques of vehicle. Wheel torque and steering input of vehicle are optimized by receding horizon optimization (RHO) and give us stable and comfort reference trajectories. In the optimization process, control inputs, tracking errors, and collision risk are to be minimized in a single objective function. Collision risk is taken into account by modeling proper potential fields that allow the controller to re-plan the given desired path for avoiding a collision. Simulation is conducted using a high-fidelity vehicle plant model and the control scheme demonstrates promising results by verifying optimal and stable path guaranteeing collision-free.
URLLC 시스템을 위한 부호화된 직교 주파수 분할 다중 방식 기반의 희소 공간-주파수 블록 코드
윤찬호(Chanho Yoon),조원철(Woncheol Cho),고영조(Young-Jo Ko) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.11
본 논문에서는 Coded OFDM 변조 신호 기반의 massive 송신 diversity 기법을 제안한다. 기존 Alamouti 송신 diversity scheme 인 최대 2개이 안테나의 한계 수에서 벗어나 subcarrier diversity 기술과 혼합하여 massive 한 antenna port 를 가지고 diversity 효과를 얻을 수 있게 한다. 모의 실험 결과 massive antenna port 를 활용할 수 있는 기존의 delay diversity 보다 성능적 우수함을 확인할 수 있고, open loop 이기에 closed loop feedback 기반의 beamforming 과 다른 짧은 latency 를 지원할 수 있다.
Effective identification of dominant fully absorbing sets for Raptor-like LDPC codes
Woncheol Cho,Chanho Yoon,Kapseok Chang,Young-Jo Ko Electronics and Telecommunications Research Instit 2023 ETRI Journal Vol.45 No.1
The error-rate floor of low-density parity-check (LDPC) codes is attributed to the trapping sets of their Tanner graphs. Among them, fully absorbing sets dominantly affect the error-rate performance, especially for short blocklengths. Efficient methods to identify the dominant trapping sets of LDPC codes were thoroughly researched as exhaustively searching them is NP-hard. However, the existing methods are ineffective for Raptor-like LDPC codes, which have many types of trapping sets. An effective method to identify dominant fully absorbing sets of Raptor-like LDPC codes is proposed. The search space of the proposed algorithm is optimized into the Tanner subgraphs of the codes to afford time-efficiency and search-effectiveness. For 5G New Radio (NR) base graph (BG) 2 LDPC codes for short blocklengths, the proposed algorithm finds more dominant fully absorbing sets within one seventh of the computation time of the existing search algorithm, and its search-effectiveness is verified using importance sampling. The proposed method is also applied to 5G NR BG1 LDPC code and Advanced Television Systems Committee 3.0 type A LDPC code for large blocklengths.